//this is the very least of what should be set within the JSON var json = { "labelExpressionInfo": {"value": "{NOM}"} };

//create instance of LabelClass (note: multiple LabelClasses can be passed in as an array) var labelClass = new LabelClass(json); labelClass.symbol = fLabel; // symbol also can be set in LabelClass' json layer.setLabelingInfo([labelClass]);

The SmartMapping class chooses appropriate colors based on the number of classes and other variables like basemap used, etc. If you want to change those colors the you should not use the SmartMapping class and manually build your class break renderer.